In a known technique which is used to join the ends of pipes, and particularly steel pipes having thin walls, one of the pipe ends is enlarged to form a bell or socket and the end of the adjoining pipe is telescopically inserted into that socket. A ring having a frusto-conical inner surface is then pressed axially along the pipe over the outer surface of the bell, the conical surface pressing the outer, belled, pipe end inwardly against the inner pipe, deforming both pipe ends and creating a tight connection between the two pipes. This technique for connecting pipes has been known for a number of years and results in a tight and long lasting pipe joint. Pipe joints of this type are described, for example, in French Pat. No. 1,140,797.
The formation of such joints has posed some problems due to the high pressures and forces required for such connections. Since the necessary force for steel pipes with an outer diameter of from 10 to 35 millimeters lies between 1 and 3 tons, the use of hand tools for forcing the ring over the bell is practically impossible.
In U.S. Pat. No. 3,474,519 an hydraulic tool for moving two rings over a pipe bell is shown, referring particularly to FIG. 9. The tool shown therein is fork-shaped and is provided with two prongs, one of which is supported on the other one and is swingable by means of a hydraulic drive unit toward and away from the other one. Both tips of the prongs are provided with partially ringshaped elements to be applied to two end surfaces of the rings.
This existing tool has the disadvantage, among others, that it is designed for simultaneous mounting of two rings, and, therefore, cannot be employed for mounting one ring only. Furthermore, the tips of the prongs describe an arc of a circle during the pressing action with the result that the pressure on the end surfaces of the rings varies. Therefore, it is possible for the rings to be pressed at a sloping angle relative to the pipe, axis, and it is also possible for the pipe to be pressed inwardly irregularly along its circumference.
A further disadvantage is the fact that all of the elements of the tool are formed as a unitary assembly so that the tool can be used for one certain pipe diameter only. Thus, for each different pipe diameter, it is necessary to use a different tool. Also, application of the tool to pipes having T-shaped branching elements is not possible. In the case of wear or damage of the fork elements, it is necessary to replace the entire tool. As will be recognized, when pipes are being laid at a construction site, separate tools for the different pipe diameters must be brought to the site.
Due to the design of the tool, e.g., the long, fork-shaped elements and the forces acting thereon, and because of the fact that the elements cannot be separated from the rest of the tool, the assembly is rather heavy and bulky.